How Does the Rain Frame Affect Perception of a Ball Falling Off a Cliff?

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Discussion Overview

The discussion revolves around the perception of a ball falling off a cliff within the context of a rain frame. Participants explore the implications of proper and geometric acceleration in this scenario, considering how the motion of the ground and the raindrop interact from different frames of reference. The scope includes theoretical reasoning and conceptual clarification regarding acceleration and perspective in a gravitational context.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant describes a scenario where a raindrop falls straight down, suggesting that from the rain's perspective, the ground appears to accelerate upwards due to a pseudo force associated with gravity.
  • The same participant questions why the situation changes when a ball rolls off a cliff, pondering whether the ground must move away to ensure the ball falls before the raindrop reaches the ground.
  • Another participant points out a note below an image, implying it may contain relevant information.
  • There is a repeated inquiry about the necessity for the floor to accelerate down first from the rain's viewpoint, indicating a lack of clarity on this point.
  • A later reply asserts that the frame of reference should be that of a free-falling ball rather than the raindrop, suggesting a shift in perspective is needed for understanding the dynamics involved.

Areas of Agreement / Disagreement

Participants express differing views on the correct frame of reference and the implications of acceleration in the context of the rain frame. There is no consensus on the necessity of the ground's motion relative to the raindrop and the ball.

Contextual Notes

Participants reference concepts of proper and geometric acceleration, but there are unresolved questions regarding the assumptions made about frames of reference and the nature of the forces involved.

FallenApple
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Shellframe.gif


So a ball is rolling off a cliff. The red is the proper acceleration and the blue is the geometric acceleration. How is it in the rain frame that the surface is moving down initially?

Consider the situation where a rain drop falls straight down, with no ball rolling, just the ground right below. When the raindrop falls, since gravity is a pseudo force, we can consider the raindrop as stationary and the floor as accelerating upwards to meet the raindrop. This makes sense because the surface of floor will have an unbalanced pressure from the bottom pushing to the top, making the patch on the surface have a proper acceleration vector of up, accelerating it though spacetime to meet the rain drop. Hence from the rains perspective, the ground needs to be seen moving up.

So why all of the sudden, when there is a ball rolling off of a cliff, the situation is changed? What if the ball is just not rolling?, then the ground would be accelerating away from the raindrop forever, which doesn't make sense.

Is it because the water drop has to hit the floor of the top of the cliff after the ball has fallen off in order for the whole frame to be internal? So while the water is in free fall, the ball still needs to fall off first. Could this mean that the whole floor has to move away to make sure that the ball leaves the cliff before the floor converges with the raindrop in spacetime?

Here is the site

https://en.wikipedia.org/wiki/Proper_acceleration
 
Last edited:
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Did you read the note below the image?
 
Orodruin said:
Did you read the note below the image?
Yes. But it didn't explain why from the viewpoint of the rain, the floor must accelerate down first.
 
FallenApple said:
Yes. But it didn't explain why from the viewpoint of the rain, the floor must accelerate down first.
As said in the note, it is not the frame of a rain drop, rather it is a frame of a free falling ball that starts moving upwards in the Earth frame.
 

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